The present invention relates to a sheet processing apparatus and an image reading apparatus provided with the same. In particular, it relates to a sheet bundle folding process.
Conventionally, image forming apparatuses, such as copiers, printers, facsimile machines and other devices using a combination of these machines, are equipped with a sheet processing apparatus that stacks sheets discharged from the image forming apparatus and that folds sheet bundles that have been stacked.
As a sheet processing apparatus that folds such sheet bundle, a folding type that employs a folding blade to press the sheet bundle between opposing and paired folding rollers, and then to draw the sheet bundle inward by rotating these folding rollers thereby folding the sheet bundle, is well known in the art.
In the conventional sheet processing apparatus that folds the sheets in this way, pass-through rollers that cover the entire width direction of the sheets are used, and the folding rollers are made of rubber or a material having a comparatively high coefficient of friction.
However, when the folding rollers having this kind of structure are used, in the sheets comprising the sheet bundle Sa, only a sheet Si which directly contacts the folding rollers 257a and 257b is pulled between the folding rollers forcefully and suddenly by the folding rollers 257a and 257b comprising a high friction coefficient, thereby causing a gap to be formed between the adjacent sheets. This situation is clearly shown in FIG. 30.
When such a gap is formed, discrepancies in the fold occur in the sheet bundle that passes through these folding rollers. To prevent such problems, the rotating speed thereof can be slowed. However, this results in a slowdown in the overall folding speed.
In view of the problems of the current technology, an object of the invention is to provide a sheet processing apparatus and an image reading apparatus equipped with the same that properly folds sheet bundle without a decrease in the folding speed.
Further objects and advantages of the invention will be apparent from the following description of the invention.